Photogrammetry delivers the goods for on-demand Quality Assurance
Envision the shop floor of an aerospace production facility. Large assemblies, workers, tools, equipment, cabling and other obstacles present major challenges for Quality Assurance personnel performing precision 3D measurements. Factor in vibration, varying temperatures, and hard-to-access areas in and around an aircraft assembly. This environment does not present laboratory conditions required by many types of CMMs and other metrology hardware.
AIRBUS-Hamburg is not a stranger to any of these encumbering QA conditions. AIRBUS was looking for a way to gather critical coordinate data with minimal impact to others working in their wake. The manufacturer has embraced photogrammetry and V-STARS technology (Geodetic Systems, Melbourne, FL) for its measure ment accuracy, and the system's high flexibility and usability in a not-so-perfect industrial set ting.
Headquartered in Toulouse, France, AIRBUS is a joint EADS Company with BAE Systems and a leading manufacturer of airliners ranging in capacity from 100 to more than 500 seats. AIRBUS utilizes the capacities and expertise of its workforce in facilities across France, Spain, Great Britain and Germany. Complete aircraft sections are produced only in Hamburg and St. Nazaire.
The V-STARS system is used 700 times a year for fuselage section interface measurements alone.
"Hamburg's share of this project is the manufacture of the front and rear fuselage sections for the AIRBUS models, including the A380. The A320 models also undergo final assembly here, which means the cockpit is joined to the middle section of the fuselage and the wings," explains Uwe Drohne, Head of Measurement Technology at AIRBUS in Hamburg.
The 15-member measurement technology team, led by Drohne, represents one division within AIRBUS Quality Assurance. This group is responsible for all jobs requiring geometric measurements. In order to perform all levels of inspection and measurement, the technicians have a number of metrology instruments at their disposal. Their arsenal ranges from stationary coordinate measuring systems to mobile laser trackers and tachymeters. When the job gets tough with obstacles galore, the Quality Assurance team reaches for their ultra-portable INCA3 Camera, the heart of the V-STARS photogrammetry system.
Photogrammetry is a 3D measuring technique that uses photographs as the fundamental medium for metrology. The V-STARS measurement system consists of one or more INCA cameras, a notebook computer with powerful, proprietary software, and various accessories that are used to capture high precision coordinate data. The entire solution can easily be carried onboard an airplane, or checked as standard baggage.
Actual measurements are acquired in digital photo/images taken from various angles. Afterward, the images are automatically processed and 3D coordinates are calculated by the advanced V-STARS software. The coordinates can be graphically displayed and analyzed by V-STARS or other inspection/analysis software. The stated measuring accuracy of the V-STARS single camera system is 5µm + 5µm/m.
The Hamburg facility alone has eight photogrammetry systems, with many others being used in other AIRBUS plants.
"In 1998, the first INCA1 system was made available to Drohne on a lease basis for one year. During that time, he and his team gathered extensive experience with the system, judged it to be good, and finally acquired one. The testing of the special applications of the camera in Hamburg was the subject of a diploma thesis. "Today, three INCA2 and five state-of-the-art INCA3 camera systems are in use in the measurement technology department," reports Roland Kinzel, General Manager of GDV Systems GmbH (Bad Schwartau), who represents V-STARS in the Germanspeaking countries.
The portability of photogrammetry is fully realized at AIRBUS.
There are two major applications of photogrammetry at AIRBUS. The first is the periodic testing of large-scale construction fixtures. These are assembly devices in which parts of aircraft sections are built. The other metrology application is fuselage section interface measurements. In addition to these two series of measurements, the quality assurance group performs many other photogrammetric mobile measurements on passenger door frames, cargo hold door frames and supports in the aircraft. Technicians also use the system to perform wing measurements and deformation measurements during testing.
Andreas Kunkel is responsible for photogrammetry in the measurement technology department. He describes the primary areas of application of the V-STARS system: "The photogrammetric V-STARS system is very well suited for measurements in unstable environments such as on a wobbly platform. The same applies to measurements in the aircraft and for measuring a large number of points. A classic example is deformation measurements where 2,000 to 3,000 points have to be measured at once."
V-STARS is also ideally suited for measurements in cases where a technician has limited access time. A good example is component and section measurements captured while workers are on their lunch break. This situation presents a window of at least 30 minutes. In that timeframe, this measurement will normally take 15 to 20 minutes to complete. The size of the photogrammetric camera also provides the answer to measuring in tight spatial conditions such as the cargo compartment of small aircraft, where a person can only move in a crouched position, and must perform measurements behind or around piping systems.
In comparison to other portable measurement devices, a photogrammetric camera requires no warm-up time and it is by nature self-calibrating. Because the INCA3 camera is light and handheld, it is particularly useful for acquiring measurements inside an object, when the fuselage is closed and you can only look inside through doors. The camera operates in two modes: online and offline. The offline mode is when the operator takes a series of photographs, then evaluates the data downstream. When used in the online mode, the camera is wireless and communicates with the computer in real-time to process data as it is captured. Both methods have their benefits, especially in remote outdoor environments where there is no electricity.
The Hamburg technicians utilize VSTARS systems several times a day, and 700 times a year for fuselage section interface measurements alone. In addition, nearly 70 construction site measurements will be taken over the course of a year, and several images will be taken per site. Add various other metrology tasks, and you easily conclude that Airbus conducts an enormous number of photogrammetric measurements. Technicians also travel with the production of an aircraft, and have to navigate through very tight enclosures. The portability and reliability of the INCA3 camera is fully realized at AIRBUS, especially in the most formidable locations on the production floor.
"The V-STARS systems have absolutely met our expectations - especially in terms of accuracy and flexibility," concludes Drohne. "We have successfully completed the measurement jobs for which the system was purchased. And we discovered various new areas of application for V-STARS. The cameras are easy to operate. After a short training period, you can hand them to someone and be off and running."
AIRBUS, an aircraft manufacturer headquartered in Toulouse, France, is a joint venture of EADS (80%) and BAE Systems (20%). The globally operating group has 55,000 employees, and claimed annual sales of a little over 20 billion Euro in 2005.
Since 1974, AIRBUS has sold more than 6,300 aircraft to approximately 250 customers and operators, and delivered more than 4,100. The AIRBUS product line currently comprises several successful aircraft families: The A320 family of standard-fuselage aircraft (A318, A319, A320 and A321), the A300/A310 family of wide-body aircraft, the A330/A340 family of long-distance aircraft, the all new A350 family and the A380 family of ultra long-distance aircraft. The capacity of the entire AIRBUS aircraft family ranges from 107 to 555 seats.airbus.com